1. Field of the Invention
This invention relates generally to digital video processing circuitry and particularly to video processing circuitry for reduction, translation and rotation of video images.
2. Description of the Prior Art
Two previous methods have been used to deal with shortcomings of video processors. One method is to add an artificial system delay during image expansion operation to match the innate video processor delay during image reduction operation. This method gives degraded system performance in the expansion and reduction modes along with simpler simulation implementation. The other method utilizes time variable control equation control parameters in the simulation controller to compensate for the time variant nonlinearities of the specified video processor. This second method gives degraded system performance in the reduction mode only.
There are several issued patents for devices related to video signal processing.
U.S. Pat. No. 3,976,982, which issued on Aug. 24, 1976 to Eiselen is directed to an apparatus for image manipulation capable of blanking an image area, combining two images, changing scale, translation, rotation, and creation of a mirror image. The apparatus uses bit stream processing for manipulating black/white images. The apparatus includes an accumulating memory for storing a base image, and external network of coded sequences, and a network that logically combines the base image with the coded sequences from the external source for manipulating an image or combining it with another image.
U.S. Pat. No. 4,233,636, which issued on Nov. 11, 1980 to Harbaugh et al. is directed to an optical read-write system with an electronically variable image size. A first laser scanner scans an object and generates an electrical signal indicative of the image of the object. The electrical image signal is stored at a read clock frequency, and the stored image signal is retrieved at a write clock frequency. The electrical image signal is then applied at the write clock frequency to a second scanner, which displays an image of the object. The size of the image compared to the object size is determined by the differential of the read clock frequency and the write clock frequency
U.S. Pat. No. 4,275,450 which issued on Jun. 23, 1981 to Potter is directed to a video magnification/demagnification apparatus and method that permits selective variation in the size of the output image derived from digital image signals.
U.S. Pat. No. 4,394,693, which issued on Jul. 19, 1983 to Shirley is directed to generating enlarged or reduced video images. Shirley discloses selective reduction or expansion of an image represented by an array of digitally valued picture elements by extracting or inserting spaced apart rows and lines of picture elements at positions that are the closest approximation to the newly scaled size. In enlargement the added lines are duplicative of the next adjacent line. In reduction the lines are deleted, and subsequent lines are shifted to close the gaps to provide a continuous image.
U.S. Pat. No. 4,417,281, which issued on Nov. 22, 1983 to Hama is directed to an image magnification control mechanism for a facsimile zoom lens. Hama discloses a position detecting section that is directly coupled to a drive member for moving the optical system of the zoom lens under the control of a servo mechanism responsive to a a pulse signal from the detecting section.
U.S. Pat. No. 4,528,693, which issued on Jul. 9, 1985 to Pearson et al. is directed to scaling facsimile image data. Pearson et al. discloses converting image data of an image matrix to a new image matrix having a different number of matrix points. Each new image pixel element (pel) has a gray scale determined by considering its position relative to the nearest neighbors of an original image pel. A look up table is addressed according to the gray scale of each neighbor pel and the position of the new pel in its neighborhood. The look up table comprises a memory organized in planes. Each plane corresponds to one of a plurality of gray scale combinations of each neighborhood. The position of each storage cell within a plane represents the position of the new pel relative to the new neighbor. By addressing a plane representing the gray scale levels within a given neighborhood and addressing a position within the represented neighborhood the gray scale of the new pel is determined.
U.S. Pat. No. 4,661,987, which issued on Apr. 28, 1987 to Anderson et al. is directed to a video processor that varies the size of a digitized video image in two video frame times by transforming successive lines of the image along one axis and then transforming successive lines of the image along the other axis.
U.S. Pat. No. 4,819,190which issued on Apr. 4, 1989 to Hinman et al. is directed to a video line processor for varying the size of a video image along a video line by varying the image size first along horizontal lines and then along vertical lines. Intermediate and final frames are stored in memories in which row and column addressing is interchanged on alternate frames.
Of particular relevance is the Statutory Invention Registration (SIR) No. H84 published Jul. 1, 1986 by Bumgardner and entitled "Real Time Polar Controlled Video Processor". This SIR discloses real time reduction, enlargement, translation, and rotation processing but with a one frame specification time delay in the reduction mode. This time delay is a potentially highly detrimental factor when viewed from the perspective of high speed missile tracking and simulation applications which are successfully addressed by the present invention. The present invention is directed to image expansion, one to one processing and image reduction as is the SIR. However, it performs operations which produce the Nyquist data base from each frame of pixels to which estimates of the desired or required gain are applied when gain estimates less than one (1) are necessary to produce the reduced next frame image from the reduced next frame without the expense of that frame time of processing required by the apparatus fo the SIR. In the SIR, as each frame to be subjected to image reduction is received, the operations performed on the received pixels to produce a Nyquist rendition of the reduced image from the lesser number of pixels resulting from the operations takes one frame-time. Thus, the present invention differs from the apparatus of the SIR in that in performing all image processing functions that the SIR does, image reduction by the present invention is performed on a per frame basis in one less frame time even though it too produces a Nyguist rendition reduced image. Further, although the present invention can be used by itself it also may be combined in those systems and devices incorporating the additional functions of direct one to one (1:1) image processing as well as image enlargement.